In FIG. 1, the structure of an aircraft comprises a fuselage 101 and a wing structure 102 which are joined together by a central box 103 referred to as the central wing box of the aircraft. The central wing box 103 notably withstands loading applied in flight to the wings of the aircraft.
The central wing box 103, and two frames 104 between which it is positioned, are depicted in FIG. 1 in heavy line. An orthonormal frame of reference in which: the axis Ox corresponds to the longitudinal axis of the aircraft, which axis extends from the tail cone to the nose cone of the aircraft; the axis Oy corresponds to the transverse axis of the aircraft, making with the axis Ox a plane that is horizontal when the aircraft is standing on a horizontal surface; and the axis Oz corresponds to the heightwise axis of the aircraft, corresponding to the vertical when the aircraft is standing on a horizontal surface, is also depicted.
FIG. 2 illustrates a detailed view of one example of a central wing box 103 oriented in space in the same way as in FIG. 1. The central wing box 103 in particular comprises: a top panel 1031, or extrados panel, extending substantially in a plane parallel to the plane (xOy), but slightly inclined and curved relative to this plane; a bottom panel, or intrados panel, extending under the top panel, substantially parallel thereto (not visible in FIG. 2); a front spar 1033, extending in a plane parallel to the plane (yOz); and a rear spar, extending behind the front spar, parallel thereto (not visible in FIG. 2).
These four components together form a volume referred to as the “volume of interest”. In general, this volume is closed laterally by two ribs referred to as end ribs, which extend one on each side of the aircraft in planes substantially parallel to the plane (xOz). In FIG. 2, only the left-hand end rib 1035 is visible. Extending inside the volume of interest are ribs, referred to as secondary ribs or internal ribs. The internal ribs extend in planes substantially parallel to the plane (xOz) or, in other words, in planes substantially orthogonal to the top and bottom panels and to the front and rear spars. The internal ribs extend parallel to any end ribs there might be. The internal ribs form reinforcing components to strengthen the wing box 103.
Other elements of FIG. 2 will be described further herein.
FIG. 3 schematically illustrates one embodiment of a secondary rib 200 according to the prior art, viewed in a plane parallel to the plane (xOz). The secondary rib 200 comprises a vertical post 201, which extends along the axis (Oz), adjacent to the front spar and outside of the volume of interest as defined hereinabove. The vertical post 201 is also visible in FIG. 2. A rib flange 202 extends adjacent to the bottom panel 1032, inside the volume of interest, whereas an on-box beam 203 extends adjacent to the top panel 1031 and outside the volume of interest (see also FIG. 2). The on-box beam 203 extends adjacent to the top panel 1031 on one side, and to a horizontal plane on the other. Rod fittings 204 project into the volume of interest and from the on-box beam. Each rod fitting 204 has two openings, each accepting a rod 205. The two rods connected to the same rod fitting extend obliquely to the rib flange 202, delineating a triangle shape therewith. A secondary rib 200 according to the prior art has, for example, six rods. FIG. 3 also depicts floor links 206 which provide the connection between the secondary rib and the floor in the aircraft. These links all have more or less the same length along the axis (Oz). A second vertical post may extend adjacent to the rear spar.
One disadvantage with the secondary ribs 200 according to the prior art is that they are complicated to install, particularly the rods 205.
One objective of the present disclosure is to allow a simplification of the installation of the internal or secondary ribs of an aircraft central wing box.